Semiconductor devices having light-emitting elements and light-receiving elements mounted on the same substrates may be found in camera modules integrated, for example, with proximity sensors and flash units for smartphones and tablet computers. A semiconductor device serving as a proximity sensor emits infrared radiation from its light-emitting element such as a light-emitting diode (LED) and detects the infrared radiation that is reflected from a target object with its light-receiving element such as a photo-diode. In this way, the semiconductor device controls an associated electronic device in response to the presence of nearby objects. Operations under such control include turning off of the liquid crystal screen when the electronic device is brought closer to a human face and turning on when the electronic device is moved away from the human face. The semiconductor device is visible through an optical window of the electronic device. Recently, however, there has been a demand for the optical windows that are as small as possible to improve the appearance of electronic devices. To meet the demand, the light-emitting element and the light-receiving element of a semiconductor device need to be mounted on the substrate as close as possible to each other to reduce the center distance between the light-emitting element and the light-receiving element in the longitudinal direction of the semiconductor device.
One document related to the present disclosure describes a semiconductor device (camera module integrated with a flash unit) configured to reduce the center distance between the light-receiving element and the light-emitting element mounted in a longitudinal direction of the device. In this semiconductor device, in a region between the light-emitting element and the light-receiving element mounted on a mounting surface of a substrate, a subset of electrodes connected to the light-emitting element alternates with a subset of electrodes connected to the light-receiving element in a short-side direction of the semiconductor device. This configuration enables the center distance between the light-receiving element and the light-emitting element to be reduced in the longitudinal direction of the device. Each electrode is electrically connected to the light-receiving element or to the light-emitting element via a bonding wire.
Unfortunately, in the semiconductor device, the bonding wires connecting the electrodes to the light-receiving element are in close proximity to the bonding wires connecting the electrodes to the light-emitting element. In addition, the light-receiving element passes a larger electric current than the light-receiving element. In this circumstance, the electric current flowing through the light-emitting element may generate noise in the light-receiving element, which may result in detection errors in the light-receiving element.
The document mentioned above is directed to a semiconductor device serving as a proximity sensor. In the manufacture of the semiconductor device, a light-transmitting resin part is formed to have a lens (primary resin molding), and a light-shielding resin part is formed to cover the light-transmitting resin (secondary resin molding) by pressing a metal mold against the entire lens surface of the light-transmitting resin part. This manufacturing method makes it possible to minimize the size of the opening to be formed in the light-shielding resin part to expose the lens surface, enabling the overall size of the semiconductor device to be reduced. However, since the metal mold is pressed against the entire lens surface, there is a risk of scratching the lens surface. Depending on the conditions of a scratch on the lens surface, the amount of incoming light and outgoing light through the lens surface may be reduced. Consequently, the performance of the semiconductor device may be reduced.
The semiconductor device described in the document mentioned above is a proximity sensor. An attempt on a semiconductor device to reduce the center distance between the light-receiving element and the light-emitting element in the longitudinal direction of the device may result in that more light emitted from the light-emitting element is reflected at the boundary plane between the optical window and the outside of the electronic device and reaches the light-receiving element. Generally, light reflected from the boundary plane between the optical window and the outside is more directive than the light reflected from a target object. Increase in the light reflected from the boundary plane between the optical window and the outside to the light-receiving element may cause the light-receiving element to determine in error that a target object is in proximity to the electronic device. Consequently, the detection accuracy of the light-emitting element may be reduced.